The term “biodiesel” is used to refer to vegetable or animal fat, oil or grease derived diesel, consisting of long-chain alkyl methyl (ethyl or propyl) esters. Biodiesel is distinct from petroleum diesel (also known as petrodiesel or petroleum derived diesel), which is a specific fractional distillate of petroleum fuel oil.
Biodiesel is typically produced from a variety of feedstocks, including edible and non-edible fats and oils. Fats are triglycerides (triesters of glycerol and any of several fatty acids), and may be either solid or liquid at room temperature. Oils are neutral, non-polar molecules with a high hydrocarbon content. Greases are semisolid lubricants which generally consist of a soap emulsified with mineral or vegetable oil. Greases can be of natural origin, and can be either vegetable or animal derived.
Many of these feedstock fats and oils have high purity, and therefore can be easily converted to biodiesel in a predictable way using known processes and known reaction conditions. However, in general pure feedstocks are more costly, the feedstocks having other potential uses.
There is also available a variety of poor quality and less pure sources of fats and oils (and greases), which can potentially be used to produce biodiesel. However, impure feedstocks are generally more problematic, leading to unpredictable reaction conditions and a less pure, less predictable biodiesel product. Fuels are required to have a certain degree of purity in order to be usable.
For example, biodiesel needs to have a certain purity or FAME (fatty acid methyl ester) value in order to be usable in engines or the like. Current legislation (EN 14214) states that in order to be suitable for use in engines, biodiesel must have a minimum ester content of 96.5%. In general, the starting material used has a large impact on the quality of the biodiesel obtained.
Therefore, due to the impure and unpredictable nature of poor quality feedstocks, it has not been practicable to use such feedstocks as a source of fats and oils (and greases) for producing fuels such as biodiesel.
In addition, existing processes for producing biodiesel are lengthy, and it would be impracticable to increase the throughput time for the production of biodiesel from a feedstock. Furthermore, it would be beneficial to reduce the time taken for the existing biodiesel production process.
It is an object of the present invention to overcome or mitigate at least some of the problems of the prior art.